1. Field of the Invention
The present invention generally relates to information processing apparatuses, profile data creating methods, display units and storage mediums, and more particularly to an information processing apparatus, a profile data creating method and a display unit which are suited for generating a profile of the display unit, and to a computer-readable storage medium which stores a program suited for causing a computer to generate the profile of the display unit.
Due to the popularization of high-performance personal computers and inexpensive image input and/or output (input/output) devices such as scanners and printers, there are increased opportunities to process color images not only for business use but also for personal use. As the opportunities to process color images increase, the color reproducibility becomes a problem. In other words, there is a problem in that the color of the image displayed on a display screen of a display unit or the color of the image printed by a printer cannot be reproduced with the same color as the original image. Among different input/output devices, color characteristics such as a color generating mechanisms and a color reproduction region differ, thereby causing the problem described above.
A Color Management System (CMS) is a technology for matching the manners in which the color is visible among the different input/output devices. By use of the CMS, it becomes possible to match the manners in which the color is visible between an image read by a scanner and an image displayed on the display unit or, between an image printed by the printer and the image read by the scanner or the image displayed on the display unit. By use of the CMS, it is possible to build a system which will not make a user feel uncomfortable or unnatural with respect to the image.
Recently, for example, Image color Matching (ICM) 1.0 of Windows 95 and ColorSync 2.0 of Macintosh (both registered trademarks) have the CMS framework built into the operating system (OS) level. Manufacturers of the input/output devices provide device profiles matching the ICM 1.0, the ColorSync 2.0 or the like with respect to the users, so that it is possible to obtain images which will not make the users feel uncomfortable or unnatural with respect to the images obtained among the different devices, such as the image displayed on the display device and the image printed by the printer. The device profiles matching the ICM 1.0, the ColorSync 2.0 or the like is in conformance with an International Color Consortium (ICC) profile proposed by the ICC. Accordingly, by providing profiles in conformance with the ICC profile specifications, manufacturers of the input/output devices can make it possible for the users in the Windows environment and the users in the Macintosh environment to use the profiles in a similar manner and to obtain images which will not make the users feel uncomfortable or unnatural with respect to the images obtained among the different devices.
2. Description of the Related Art
When carrying out the CMS in the conventional computer environment, the ICC profile is generally used as information containing characteristics of the input/output device. FIG. 1 is a diagram for explaining the structure of the ICC profile. In the ICC profile, the necessary data are all described by tags. As shown in FIG. 1, the ICC profile is made up of a profile header indicating information of the profile itself and information of a target input/output device, a tag table indicating kinds of information stored, and a tagged element data actually storing information. The profile header has a fixed length of 128 bytes. The tag table has a variable length of (4+12n) bytes with respect to n which indicates the number of tags, and includes an identifier, a storage address and a size. The tagged element data has a variable length, and contains information indicating the characteristics of the input/output device.
FIG. 2 is a diagram showing a CIE XYZ uniform color space, and FIG. 3 is a diagram showing input/output characteristics of each of the colors read (R), green (G) and blue (B). In FIG. 3, the ordinate indicates a displayed luminance in arbitrary units, and the abscissa indicates an input voltage in arbitrary units.
It is possible to know a display characteristic of a display unit which is one example of the input/output device, from CIE XYZ values of the colors R, G and B shown in FIG. 2 when the colors R, G, and B respectively have maximum values Rmax, Gmax and Bmax (white Wmax), and from the input/output characteristics of the colors R, G and B shown in FIG. 3. The CIE XYZ values of the colors R, G and B shown in FIG. 2 are called a color reproduction range CR related to colors which can be discriminated by the human eye, and the input/output characteristics of the colors R, G and B shown in FIG. 3 are called xcex3-characteristics.
The CIE XYZ values of the colors R, G and B are stored in rXYZ, gXYZ and bXYZ tags of the ICC profile for the display unit, as information of the color reproduction range CR. In addition, input/output point values of the colors R, G and B are stored in rTRC, gTRC and bTRC tags of the ICC profile as the xcex3-characteristics. In the ICC profile, it is indicated that a xcex3-coefficient of the color is 1.0 when the number of points within the tag is 0, and the value of the xcex3-coefficient itself is stored when the number of points is 1. Moreover, when the number of points within the tag is 2 or greater, the same number of input/output point values are stored in the ICC profile. Furthermore, in the ICC profile, the CIE XYZ value when the white has the maximum value Wmax is stored in a wtpt tag as standard white information of the display unit. Each of the tags described above is stored in the ICC profile shown in FIG. 1 as the tag element data.
Therefore, the 7 kinds of information described above are generally stored in the ICC profile of the display unit. The 7 kinds of information can be obtained by displaying color data on the display unit and measuring the displayed luminance and the CIE XYZ values by a color measuring device such as a spectral radiance measuring device.
In display units such as a Plasma Display Panel (PDP) having a high power consumption, a power control is carried out to suppress the power consumption. In other words, an applying voltage applied to the PDP is reduced in a case where the power consumption is large such as when making a display which includes a large amount of white, and the applying voltage applied to the PDP is increased in a case where the power consumption is small such as when making a display which includes a large amount of dark colors such as gray and blue, so as to control the voltage applied to the PDP so that dark colors are displayed more brightly. In the display unit which carries out such a power control, measured results may indicate that the displayed luminance of blue is brighter than the displayed luminance of white.
FIGS. 4 and 5 are diagrams showing measured results of actual displays on the display unit. FIG. 4 shows the measured results of the display unit which controls the applying voltage, and FIG. 5 shows the measured results of the display unit which does not control the applying voltage. More particularly, FIG. 4 shows the measured result of the PDP, and FIG. 5 shows the measured results of a CRT.
In the measured results shown in FIG. 4, the X value of red is greater than the X value of white, and the Y value of green is greater than the Y value of white, for example. On the other hand, in the measured results shown in FIG. 5, a relationship R(X, Y, Z)+G(X, Y, Z)+B(X, Y, Z)=W(X, Y, Z) stands.
In the display unit, the color reproduction range information and the standard white information are used on the precondition that the additive mixture of color stimuli stands. For this reason, there was a problem in that it is impossible to create the profile of the display unit from the measured results shown in FIG. 4 in which the additive mixture of color stimuli does not stand. In other words, the color reproduction range information and the standard white information must be measured under the same conditions, but in the display unit which carries out the power control described above, the applying voltage is freely controlled, for example, thereby changing the conditions such as the applying voltage depending on the displayed color. Because the measurements are not made under the same conditions when the power control is carried out, it is impossible to create the profile of the display unit from the measured results.
On the other hand, in the PDP, a slight light emission may occur even when displaying black, due to the structure of the PDP. This slight light emission is sometimes referred to as a back light emission which causes considerably errors when creating the profile.
Accordingly, it is a general object of the present invention to provide a novel and useful information processing apparatus, profile data creating method, display unit and storage medium, in which the problems described above are eliminated.
Another and more specific object of the present invention is to provide an information processing apparatus, profile data creating method, display unit and storage medium, which enable a profile of the display unit to be created from measured results of the display made on the display unit, even in the case of a display unit which carries out a power control or the like and the same measuring conditions cannot be set by a user.
Still another object of the present invention is to provide an information processing apparatus comprising a color display simultaneously displaying a reference color patch and at least one measuring color patch which is to be measured. According to the information processing apparatus of the present invention, it is possible to create the profile of a display unit from the measured results of the colors of the color patches displayed on the display unit, even in the case of the display unit which carries out a power control or the like and the same measuring conditions cannot be set by a user.
A further object of the present invention is to provide a computer-readable storage medium which stores a program for causing a computer to display an image, comprising color display means for causing the computer to simultaneously display on a display unit a reference color patch and at least one measuring color patch which is to be measured. According to the storage medium of the present invention, it is possible to create the profile of the display unit from the measured results of the colors of the color patches displayed on the display unit, even in the case of the display unit which carries out a power control or the like and the same measuring conditions cannot be set by a user.
Another object of the present invention is to provide a display unit comprising a display screen, wherein the display screen displays a reference color patch which is used as a reference color, and at least one measuring color patch of a color different from that of the reference color patch. According to the display unit of the present invention, it is possible to create the profile of the display unit from the measured results of the colors of the color patches displayed on the display unit, even in the case of the display unit which carries out a power control or the like and the same measuring conditions cannot be set by a user.
Still another object of the present invention is to provide a profile data creating method for creating a profile data which is used to correct a display characteristic of a display unit corresponding to an input color signal, comprising a displaying step displaying, on a screen of the display unit, a reference color patch which is used as a reference color, and a measuring color patch of a color different from that of the reference color patch, a calculating step calculating a ratio of a measured value of the reference color patch and a measured value of the measured color patch which are measured from the screen, and a creating step creating a profile data based on the calculated ratio of the measured values. According to the profile data creating method of the present invention, it is possible to create the profile of the display unit from the measured results of the color patches displayed on the display unit, even in the case of the display unit which carries out a power control or the like and the same measuring conditions cannot be set by a user.
A further object of the present invention is to provide a profile data creating method for creating a profile data which is used to correct a display characteristic of a display unit corresponding to an input color signal, comprising a calculating step calculating relative values of a measured value of a reference color patch which is used as a reference color, and a measured value of a measuring color patch of a color different from that of the reference color patch, and a creating step creating a profile data based on the calculated relative values. According to the profile data creating method of the present invention, it is possible to create the profile of the display unit from the measured results of the color patches displayed on the display unit, even in the case of the display unit which carries out a power control or the like and the same measuring conditions cannot be set by a user.
Other objects and further features of the present invention will be apparent from the following detailed description when read in conjunction with the accompanying drawings.